The Sixth International Workshops on Opportunistic Protists will be held concurrently with the annual meetings of The Society of Protozoologists in Raleigh, North Carolina, May 26-29, 1999. The focus of these workshops will be on the AIDS-related opportunistic infectious protists, Pneumocystis, Cryptosporidium, Toxoplasma and the microsporidia. These workshops, sponsored by The Society of Protozoologists, have evolved from the 1st in Bristol, U.K., 1988 (limited to Pneumocystis), 2nd in Bozeman, Montana, 1991 (which incorporated Cryptosporidium and the microsporidia), 3rd in Cleveland, Ohio, 1994 (which included Toxoplasma), 4th, the most recent in the USA, was held in Tucson, Arizona, 1996), and 5th in Lille, France, 1997. The organisms to be discussed at these scientific meetings are responsible for much of the morbidity and mortality in immunocompromised individuals. As part of the Society of Protozoologists 1999 annual meetings, a symposium on "Emerging Opportunistic Protists" is being organized; this will nicely complement the Workshops. Although other meetings sponsored by other organizations have had symposia and special sessions on one or several of these opportunistic pathogens, the Workshops on Opportunistic Protists have become the mechanism by which many investigators gather for obtaining comprehensive information focusing on these four organisms. The rapid publication of short communications resulting from these workshops in The Journal of Eukaryotic Microbiology ensures efficient dissemination of up to date information on progess being made on these pathogens and the diseases they cause. One of the outstanding features of these workshops is that participation (presentations by platform or poster) is open to anyone wishing to present their findings; the only requirement being registration and attendance. A limited number of young investigators, women and individuals from underrepresented ethnic backgrounds, in addition to heads of laboratories working at the forefronts are invited, with their expenses partially reimbursed by the workshop funds generated by the organizers. Most major laboratories working on these organisms have participated in previous workshops.